258 CHARLES C. FITZMORRIS 



in canals dug for the purpose. A series of these water turbines 

 has been installed at Niagara falls in such a position that they 

 receive the impact of water after a fall of 136 feet. These 

 turbines are all of 5,000 horsepower. Other forms of water 

 turbines resemble closely the ancient water wheels. These 

 wheels, formed similarly to the wheel in the steam turbine, 

 are placed in streams or beneath falls to receive the impact 

 of the water and develop an extraordinary number of horse- 

 power. A three foot wheel, receiving water from one nozzle, 

 which delivered a half inch stream under a water head of 

 2,100 feet, developed 100 horsepower. 



There are tidal and wave engines that depend for their 

 power upon the movements of the tides and the waves, but 

 these, besides being capable of operation only at intervals, are 

 expensive, complicated, and easily damaged, and, exposed 

 as they are to the elements, are constantly in need of repairs. 



The mostly widely known engine after the steam engine, 

 and probably better known than the turbine, is the gas engine, 

 which works much after the manner of the reciprocating 

 steam engine. Its power is furnished by the explosion of a 

 mixture of gas and air in the cylinder. The gas, manu- 

 factured previously, or formed from gasoUne, or some other 

 substance in the cylinder, is admitted together with a quantity 

 of air. The mixture is exploded by an electric spark and 

 force is developed that drives the piston rod forward. A fly 

 wheel controls the speed to a certain extent and keeps it 

 steady. The common form of gas engine receives an impact 

 against the piston head but once during each complete strike. 

 Other forms of engines, however, receive the impact every 

 other stroke of the cylinder, while in a new form, the double 

 acting gas engine, the gas is admitted at the center of the 

 cyhnder, making it double acting — on the same principle as 

 the steam engine after which it is patterned. 



The gas engine is being built larger every year, cliiefly 

 because of the fact that gas is a much cheaper source of power 

 than coal. New forms of gas have been invented recently 

 and this has added to the economy of the gas engine. An 

 Allis-Chalmers gas engine of 2,000 horsepower was exhibited 

 at the St. Louis world's fair, while another, of German make, 



